Actually if you are a brother you really shouldn't have such images at all (of people -either male or female) - this can create fitnah for yourself - so if i was you i would try to avoid it.
If you are a sister however, this can also create fitnah - so i would also recommend not to have such images on your phone.
These pictures are however quite sexual (im a female btw and i dont have lesbian tendencies).Even if some arent sexual, you should know that the non-muslims have different agendas to us - they dont focus on hayya (shyness) and so by looking at these pictures casually you may lose your hayya and look at real women without hayya and therefore you might not act modestly towards them but rather casually! This then creates a huge fitnah!
Besides this, yes, making pictures is haraam an should be avoided unless their is a necessity. For example, if this is used as evidence for a crime, proof of a wedding, etc. i believe that it is allowed. Please do double check this however.
The scholars say that making pictures is haraam and this ranges to taking photographs of animate objects (which the scholars do dispute whether or not this is haram) to painting/ drawing animate objects on a paper (which is haram) to building physical objects i.e. statues of animate objects e.g. lions, etc.
It should be noted that matters pertaining to the photography of animate objects is a doubtful area so it is better to not take pictures of these objects but you can take pictures of inanimate objects e.g. the sky.
a) Even if your friends dont care, you should, if these friends of yours arent helping you get closer to Allah then these may bring you closer to jahanam
this is not the friendship you want to have!
b)we aren't allowed to make pictures but we are allowed to view them (so long as these arent inappropriate - especially if they are of people - same sex or not this can create fitnah
Allah tells us to lower our gaze!
Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do.
And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their headcovers over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.
c)if images are promoting haram acts try not to look at them
d)if the images are electronic and promote haram things still try not to look at them but you can look at images. For example, if you see a cat picture and your immediate reaction is "aw" or "subhanallah" etc. thats fine you can look at these pictures electronic or not
e) Yes i believe you can read the Quran without wudu on electronic devices such as a phone laptop etc.
And Allah knows best